The present invention relates to a transmission and a drive unit for a muscle-powered vehicle having an auxiliary motor, in particular for a pedelec, comprising a housing which can be fitted on the vehicle, a first drive shaft mounted in the housing for feeding in muscle power, said first drive shaft being coupled to an approximately coaxial output shaft for driving the vehicle, and further comprising, approximately at a right angle to said first drive shaft, a second drive shaft for connecting the auxiliary motor, which second drive shaft acts on the output shaft via an angular gear. The invention also relates to a muscle-powered vehicle having such a drive unit.
With muscle-powered vehicles having an auxiliary motor, the muscle power drive and auxiliary motor drive should be able to drive the vehicle both independently of one another and jointly, in a manner assisting one another. If the vehicle is a bicycle having an electric auxiliary motor, it is also referred to as a “pedelec”. By way of example, pedelecs with wheel hub auxiliary motors are known, which can also be operated by muscle power via conventional treadles (pedals) and chain drive. Since such wheel hub auxiliary motors have to apply a relatively high torque due to the low rotational speed of the wheels, they are large and heavy.
WO 2011/113642 presents a bicycle having an auxiliary motor, in which both the pedals and the auxiliary motor act via a transmission on a common output shaft, by means of which a chain drive drives the wheel. The axes of all transmission and drive parts are parallel to one another here. Due to the intermediate transmission, the motor can indeed be smaller, however, due to the narrow space between the two pedals, a motor of conventional design can hardly be considered due to its overall length; a disc-armature motor better suited for this, as is also used in wheel hub motor drives, either has an air core however and is therefore less efficient or is equipped on its rotor periphery with permanent magnets and is therefore relatively heavy.
A transmission of the type mentioned in the introduction is described in EP 1 878 650. This document discloses an elongate auxiliary motor, which is integrated into the vehicle frame and acts via an angular gear on the crankshaft, on which the pedals also sit. The angular gear is a bevel gear, which impairs the initial setting of the pedelec during manufacture and the readjustment of the transmission during use: in the case of bevel gears, the gear play is to be set at both shafts in both axial directions thereof and this therefore cannot be implemented easily.